Power supply systems are pervasive in many electronic applications from computers to automobiles. Generally, voltages within a power supply system are generated by performing a DC-DC, DC-AC, and/or AC-DC conversion by operating a switch loaded with an inductor or transformer. One class of such systems includes switched mode power supplies (SMPS). An SMPS is usually more efficient than other types of power conversion systems because power conversion is performed by controlled charging and discharging of the inductor or transformer and reduces energy lost due to power dissipation across resistive voltage drops.
A SMPS usually includes at least one switch and an inductor or transformer. Some specific topologies include buck converters, boost converters, and flyback converters, among others. A control circuit is commonly used to open and close the switch to charge and discharge the inductor. In some applications, the current supplied to the load and/or the voltage supplied to the load is controlled via a feedback loop.
One of the factors that determine the efficiency of a SMPS is the amount of power consumed by the switching transistor that is used to implement the switch in the SMPS. As the switching transistor is turned on, any current that flows through the switching transistor is dissipated through the switching transistors. Thus, the higher the voltage across the switching transistor when the transistor is conducting current, the higher the power dissipated through the switching transistor.